"For one thing, the researchers did not show that the release of adenosine was specific to acupuncture. Acupuncture needles might cause adenosine to flood the surrounding tissue, but so might a hard pinch, or applied pressure, or any number of other physical insults. In fact, both of the studies found that when adenosine was turned on in mouse tissue by other mechanisms, the pain response was equal to or better than the response generated by acupuncture."
From a Scientific American article currently titled "Research Casts Doubt on the Value of Acupuncture/Scientific studies show that the procedure is full of holes."
(The original title was "The Acupuncture Myth." I'm contemplating why the title was changed and thinking the magazine has some standards about what counts as a "myth" and that if you have utterly disproved something you are not yet in a position to call it a myth.)
ADDED: This article made me wonder how scientists can determine the extent to which a mouse feels pain. It can't point to one of the 10 pain faces on the chart. I found this article in Wired: "Mice Show Pain on Their Faces Just Like Humans":